Isocitrate dehydrogenases (IDHs) catalyze the oxidative decarboxylation of isocitrate to 2-oxoglutarate (i.e., α-ketoglutarate). These enzymes belong to two distinct subclasses, one of which utilizes NAD(+) as the electron acceptor and the other NADP(+). Five isocitrate dehydrogenases have been reported: three NAD(+)-dependent isocitrate dehydrogenases, which localize to the mitochondrial matrix, and two NADP(+)-dependent isocitrate dehydrogenases, one of which is mitochondrial and the other predominantly cytosolic. Each NADP(+)-dependent isozyme is a homodimer.
IDH1 (isocitrate dehydrogenase 1 (NADP+), cytosolic) is also known as IDH; IDP; IDCD; IDPC or PICD. The protein encoded by this gene is the NADP(+)-dependent isocitrate dehydrogenase found in the cytoplasm and peroxisomes. It contains the PTS-1 peroxisomal targeting signal sequence. The presence of this enzyme in peroxisomes suggests roles in the regeneration of NADPH for intraperoxisomal reductions, such as the conversion of 2,4-dienoyl-CoAs to 3-enoyl-CoAs, as well as in peroxisomal reactions that consume 2-oxoglutarate, namely the alpha-hydroxylation of phytanic acid. The cytoplasmic enzyme serves a significant role in cytoplasmic NADPH production.
The human IDH1 gene encodes a protein of 414 amino acids. The nucleotide and amino acid sequences for human IDH1 can be found as GenBank entries NM_005896.2 and NP_005887.2 respectively. The nucleotide and amino acid sequences for IDH1 are also described in, e.g., Nekrutenko et al., Mol. Biol. Evol. 15:1674-1684 (1998); Geisbrecht et al., J. Biol. Chem. 274:30527-30533 (1999); Wiemann et al., Genome Res. 11:422-435 (2001); The MGC Project Team, Genome Res. 14:2121-2127 (2004); Lubec et al., Submitted (December 2008) to UniProtKB; Kullmann et al., Submitted (June 1996) to the EMBL/GenBank/DDBJ databases; and Sjoeblom et al., Science 314:268-274 (2006).
Non-mutant, e.g., wild type, IDH1 catalyzes the oxidative decarboxylation of isocitrate to α-ketoglutarate thereby reducing NAD+ (NADP+) to NADH (NADPH), e.g., in the forward reaction:Isocitrate+NAD+(NADP+)→α-KG+CO2+NADH(NADPH)+H+.
It has been discovered that mutations of IDH1 present in certain cancer cells result in a new ability of the enzyme to catalyze the NAPH-dependent reduction of α-ketoglutarate to R(−)-2-hydroxyglutarate (2HG). The production of 2HG is believed to contribute to the formation and progression of cancer (Dang, L et al, Nature 2009, 462:739-44).
The inhibition of mutant IDH1 and its neoactivity is therefore a potential therapeutic treatment for cancer. Accordingly, there is an ongoing need for inhibitors of IDH1 mutants having alpha hydroxyl neoactivity.
PCT Publication No. WO 2013/107291 and US Publication No. US 2013/0190249 hereby incorporated by reference in their entirety, disclose compounds that inhibit IDH1 mutants (e.g., IDH1R132H or IDH1R132C). These applications additionally disclose methods for the preparation of inhibitors of mutant IDH1, pharmaceutical compositions containing these compounds, and methods for the therapy of diseases, disorders, or conditions (e.g., cancer) associated with overexpression and/or amplification of mutant IDH1.
There is a need for pharmaceutical compositions that would have properties suitable for large-scale manufacturing and formulation, as well as utility in treating advanced hematologic malignancies, such as acute myelogenous leukemia (AML), myelodysplastic syndrome (MDS), myeloproliferative neoplasms (MPN), myeloproliferative neoplasms (MPN), chronic myelomonocytic leukemia (CMML), B-acute lymphoblastic leukemias (B-ALL), or lymphoma (e.g., T-cell lymphoma), each characterized by the presence of a mutant allele of IDH1.